1885.] 



in the Tentacles of Drosera dichotoma. 



233 



becoming porous, and that the method of establishing a loss of 

 turgidity by solutions of neutral salts and the like involves a state of 

 things essentially different from that which normally occurs. - In 

 the one case the protoplasm itself undergoes change. In the other 

 the cell sap is violently abstracted by artificial means from the 

 vacuole of a protoplasmic utricle which is endeavouring to protect 

 itself from the action of the reagent. 



Movements of the tentacles may be brought about by direct contact 

 and by cutting or injury, by electric stimulus, by the addition or 

 withdrawal of water, and especially by the stimulus of food. In 

 all these cases the stimulant upsets the existing equilibrium and 

 brings about a difference of turgidity on the two opposite sides. Loss 

 of water by plasmolysis usually induces movement, unless the salts 

 employed have a specific action upon the protoplasm. Movement 

 may occur without aggregation, and secretion may occur without 

 movement, bat whenever well-defined aggregation takes place, move- 

 ment always follows. Different strengths of the same reagent may 

 bring about different reactions. Thus a 0*1 per cent, solution of 

 chromic acid causes both movement and secretion, while with a 

 I or 2 per cent, solution neither ^phenomenon occurs. Among the 

 curious effects of various salt solutions that of ammonic chloride may be 

 noted, in that it acts markedly as a sedative, toning down aggregation 

 and restoring turgidity. It was very generally noticed that the ten- 

 tacles before becoming inflected, moved downwards and backwards, 

 and that the upward and inflected movement subsequently took place. 

 When a tentacle has become well inflected it can be observed that at 

 the bending point the cells of the convex side are very turgid, with their 

 plastoids spindle shaped, and that little or no aggregation has taken 

 place, while in the cells of the concave side, on the other hand, there is 

 well-marked aggregation and loss of turgidity ; the aggregation after a 

 time extends to the convex side, the cells of which, in their turn, lose 

 their turgidity, and at this stage all rthe cells are flaccid. Later on" 

 the cells of the concave side first regain their turgidity, and now the 

 tentacle is bent back to its original position before stimulation. From 

 certain observations on Dionasa and Mimosa, the author is led to 

 believe that there also movement is made possible by the establishing 

 of sudden and different conditions of turgidity of different cells, such 

 differences being occasioned by the induced porosity of the protoplasm 

 of certain of these cells. These phenomena occur perhaps in all cases 

 of movement. 



The plastoid markedly decreases in size after long stimulation 

 in both Dionaea and Drosera. There are therefore some grounds for 

 believing that it consists mainly of some reserve material or some 

 substance which is used up during secretion. Whether the crystal- 

 loids in the nucleus of Pinguicula serve a similar purpose remains to 



